Majuscules and minuscules.

Roman style

The Romans had several styles of writing: square capitals, rustic capitals, and cursive. None of them made use of the modern mixed-case system, where the bulk of the text is in minuscules and majuscules serve as capitals; the alphabet for the Romans was a single-case system, like Hebrew or Korean. The most Roman style, then, would be to use a single-case system, which is not without its issues, of which thechoice of case is probably the most important: a single-case system requires the decision to use either majuscules or minuscules exclusively, or the institution of rules to decide which are to be used in what situations. (Either case would be valid; our majuscules descend from the Roman square capitals, and our minuscules from the Roman cursive.) Each case has its own drawbacks: majuscule text is more difficult to read, and minuscule text may confuse the reader by discarding capitals they are used to expecting. The choice of case may have further effects elsewhere (e.g. in the choice of V vs. u.)

Modern style

Modern languages use varying systems of capitalization for mixed-case text. The most widespread conventions are, perhaps, the capitalization of the first letter of a sentence, and that of proper nouns naming people, places, and things. Less universal are practices such as the capitalization of proper nouns naming intangibles (such as names of religions, which are capitalized in languages such as English, but not in French), the capitalization of common nouns (as in German and older English, but not in modern English), and the capitalization of adjectives, common nouns, and other parts of speech when their sense refers to proper nouns (as ‘English,’ but not ‘español’). Modern trade names often use mixed case for a distinctive effect.

The rule capitalizing the initial letter of a sentence should be retained for recognizability and proximity to modern use of the script. ‘Internationalized’ words have conventions that may vary from language to language, and should, for Latin, be treated under the same rules as native Latin words. Words derived from languages without casing scripts should also be treated under the same rules as Latin words. Words derived from a particular language using a casing script—including words derived from other Latin words—would by the same principle retain the capitalization of the original word.

Six rules help us determine whether a term should be capitalized or not:

If the term is used at the beginning of a sentence, it should be capitalized, according to universal practice in modern European languages.

Otherwise, if the term is derived from a term in another language that is capitalized, or from another term in Latin that would be capitalized by these rules, then it should remain capitalized; we assume no authority to institute a change.

Otherwise, if the term is not a proper name, it should not be capitalized. (This is perhaps the most difficult rule, as people are very often taught to recognize proper names orthographically, not semantically.)

Otherwise, if the term does not refer to a person, place or physical object, it should not be capitalized.

Otherwise, if the term is a noun, capitalize it.

If none of the above apply, it should not be capitalized.

Side effects:

Semantic sets may exert pressure for all their members to be capitalized alike. In some cases this passes unnoticed (in English Marxism is written, but communism need not be capitalized) but when this differs from the practice of other languages it may appear awkward: these rules would—on the same principle as the English example—produce Iudaismus from Judah and Ianuarius from Janus but islamismus from islam ‘submission’ and december from decem ‘ten’, while many if not most languages would probably apply the same capitalization to all months (enero, diciembre / January, December) and all religions (islamismo, cristianismo / Islam, Christianity). The set of sets that might want uniform capitalization is potentially open-ended, so it is beyond the scope of these guidelines to prescribe them: it is up to the editor whether to apply extra capitals for consistency or to leave them as the rules find them. (In short, capitals may be added if it is felt the rules leave them short, but they should not be removed.)